Effects of phosphates on the expression of tissue-nonspecific alkaline phosphatase gene and phosphate-regulating genes in short-term cultures of human osteosarcoma cell lines

Abstract

We studied the effects of phosphates on the expression of the human tissue-nonspecific alkaline phosphatase (TNSALP) gene and phosphate-regulating genes in short-term cultures of human osteoblastic osteosarcoma cell lines. When human osteosarcoma cell lines, SaOS-2, MG-63, and U(2)OS were cultured with 10 mM inorganic sodium dihydrogenphosphate, 10 mM beta-glycerophosphate, 250 microM pyridoxal phosphate, or 100 microM inorganic pyrophosphate, enzymatic activity of alkaline phosphatase began to increase at 72 h after addition of sodium dihydrogenphosphate and beta-glycerophosphate in SaOS-2 cells. Pyridoxal phosphate and pyrophosphate did not induce alkaline phosphatase activity. U(2)OS cells slightly reacted to beta-glycerophosphate, but MG-63 cells did not react on exposure to phosphates. In SaOS-2 cells, TNSALP mRNA measured by real-time RT-PCR reached a peak level at 72 h after the addition of beta-glycerophosphate. PHEX and MEPE mRNAs were also induced by beta-glycerophosphate. These results suggest that TNSALP, PHEX and MEPE were concordantly induced by beta-glycerophosphate on mineralisation.